HTHL vs VTVL - Wheeled sled for landing?

Please remember that I am a VTVL fan, I am just trying to give HTHL a fair
shake but getting rid off completely the major weight problem VTVL fans claim
for HTHL.

(Len) :

If the returning vehicle is light enough and slow enough,
then I think that air recovery--perhaps with a helicopter
--is more practical than trying to line up with a sled on
the ground. As a pilot, I am much happier with a couple
of minutes, rather than ten seconds, to match speeds and line
up with the recovery vehicle.

A flying sled? Interesting idea, why not? Now you have the sink time to try
to mate up. You would have time to either do it very slowly or multiple
tries - probably both. Not there is no need for the flysled to be able to
hold the HL up, the HL already has wings, some extra thrust from the flying
sled after mating will keep the air speed up so it can continue to support
itself.

Does light weight really matter? If the catcher aircraft has beefed landing
gear/brakes/support structures to handle the weight of the HL craft then all
the catcher has to do match speeds with the HL, mate, and if needed supply
some thrust to get the HL to the runway. Think off a souped up SS1 but with
the thrusters on the bottom.

Another interesting thing about this idea is the weight of the catcher does
not have to be that high and thus not too expensive.

Relative speeds are far more important than absolute speeds.
However, this seems to scare non-pilot types a bit. Military
pilots learn to fly in tight formation at high subsonic speeds
and in almost any attitude. It's fun.

While not a pilot, I thought this would be well understood. But for some
strange reason more than one person seems to think that I don't plan to have
the landing sled pre-match the landing craft speed first before they meet
which as far as I can see would be a crazy way to land on any sort of movable
pad.

In the case of a flying sled can they be brought together without the airflow
between the two crafts messing up the fine control needed?

Earl Colby Pottinger

--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp

Earl Colby Pottinger wrote in message ...
Please remember that I am a VTVL fan, I am just trying to give HTHL a fair
shake but getting rid off completely the major weight problem VTVL fans claim
for HTHL.

(Len) :

If the returning vehicle is light enough and slow enough,
then I think that air recovery--perhaps with a helicopter
--is more practical than trying to line up with a sled on
the ground. As a pilot, I am much happier with a couple
of minutes, rather than ten seconds, to match speeds and line
up with the recovery vehicle.

A flying sled? Interesting idea, why not? Now you have the sink time to try
to mate up. You would have time to either do it very slowly or multiple
tries - probably both. Not there is no need for the flysled to be able to
hold the HL up, the HL already has wings, some extra thrust from the flying
sled after mating will keep the air speed up so it can continue to support
itself.

Does light weight really matter? If the catcher aircraft has beefed landing
gear/brakes/support structures to handle the weight of the HL craft then all
the catcher has to do match speeds with the HL, mate, and if needed supply
some thrust to get the HL to the runway. Think off a souped up SS1 but with
the thrusters on the bottom.

Another interesting thing about this idea is the weight of the catcher does
not have to be that high and thus not too expensive.

Relative speeds are far more important than absolute speeds.
However, this seems to scare non-pilot types a bit. Military
pilots learn to fly in tight formation at high subsonic speeds
and in almost any attitude. It's fun.

While not a pilot, I thought this would be well understood. But for some
strange reason more than one person seems to think that I don't plan to have
the landing sled pre-match the landing craft speed first before they meet
which as far as I can see would be a crazy way to land on any sort of movable
pad.

In the case of a flying sled can they be brought together without the airflow
between the two crafts messing up the fine control needed?

With air recovery, a tow line is an option--and that can avoid
airflow intereactions.

Back in the early 1960s, when I was project engineer for
space transportation systems at North American/LA Div.,
we looked at towing an upper stage package with the B-70
in order to avoid airflow interactions, and also to get
a bigger lump through the drag rise. The B-70 bombbay
was not large enough to carry a very big upper stage
package--although I think that the Agena fit. (Lockheed
had contacted us about launching Agena from the B-70.
Although they were interested in the performance booost,
their main motivation--even back in the early 1960s--was
an excuse to get away from the official launch complexes
like the Cape).

The early Discover(?) satellite capsules were recovered
with a C-130. This sort of worked even though the capsule
was traveling vertically (from a parachute) and the C-130
was basically traveling horizontally.

Best regards,
Len (Cormier)
PanAero, Inc.
(replace x with len) ( http://www.tour2space.com )

Earl Colby Pottinger

Earl Colby Pottinger wrote in message ...
Please remember that I am a VTVL fan, I am just trying to give HTHL a fair
shake but getting rid off completely the major weight problem VTVL fans claim
for HTHL.

(Len) :

If the returning vehicle is light enough and slow enough,
then I think that air recovery--perhaps with a helicopter
--is more practical than trying to line up with a sled on
the ground. As a pilot, I am much happier with a couple
of minutes, rather than ten seconds, to match speeds and line
up with the recovery vehicle.

A flying sled? Interesting idea, why not? Now you have the sink time to try
to mate up. You would have time to either do it very slowly or multiple
tries - probably both. Not there is no need for the flysled to be able to
hold the HL up, the HL already has wings, some extra thrust from the flying
sled after mating will keep the air speed up so it can continue to support
itself.

Does light weight really matter? If the catcher aircraft has beefed landing
gear/brakes/support structures to handle the weight of the HL craft then all
the catcher has to do match speeds with the HL, mate, and if needed supply
some thrust to get the HL to the runway. Think off a souped up SS1 but with
the thrusters on the bottom.

Another interesting thing about this idea is the weight of the catcher does
not have to be that high and thus not too expensive.

Relative speeds are far more important than absolute speeds.
However, this seems to scare non-pilot types a bit. Military
pilots learn to fly in tight formation at high subsonic speeds
and in almost any attitude. It's fun.

While not a pilot, I thought this would be well understood. But for some
strange reason more than one person seems to think that I don't plan to have
the landing sled pre-match the landing craft speed first before they meet
which as far as I can see would be a crazy way to land on any sort of movable
pad.

In the case of a flying sled can they be brought together without the airflow
between the two crafts messing up the fine control needed?

With air recovery, a tow line is an option--and that can avoid
airflow intereactions.

Back in the early 1960s, when I was project engineer for
space transportation systems at North American/LA Div.,
we looked at towing an upper stage package with the B-70
in order to avoid airflow interactions, and also to get
a bigger lump through the drag rise. The B-70 bombbay
was not large enough to carry a very big upper stage
package--although I think that the Agena fit. (Lockheed
had contacted us about launching Agena from the B-70.
Although they were interested in the performance booost,
their main motivation--even back in the early 1960s--was
an excuse to get away from the official launch complexes
like the Cape).

The early Discover(?) satellite capsules were recovered
with a C-130. This sort of worked even though the capsule
was traveling vertically (from a parachute) and the C-130
was basically traveling horizontally.

Best regards,
Len (Cormier)
PanAero, Inc.
(replace x with len) ( http://www.tour2space.com )

Earl Colby Pottinger

Earl Colby Pottinger wrote:
[...]
None of those considerations prevent the use of a land based powered landing
sled that matchs speed and ground track with the landing craft (note I don't
assume it is without any power) thus saving more weight.

Note: the feedback system to make the sled track the landing craft can be as
simple as a laser directed downwards from the base of the landing craft and a
set of sensors on the sled insure that the beam is always held in the center
of the landing sled's platform.

I suspect that at "reasonable" landing speeds, the lateral tracking of
the sled will be limited by how tight a turn it can make before it
starts tipping. Of course, a wide-and-low sled won't tip *over* very
easily, but it will probably tip enough to affect wheel loading, which
may feed into speed control as well as steering forces.

And I also suspect that the difference in speed between lander and
sled has to be *very* small to avoid in-track shear forces, and the
sled may have to be *very* heavy to avoid the lander's lift from
picking it up, which implies tensile strength for the capture.

Then there's the length of the landing strip. It needs to be long
enough to be able to brake (w/wheels or drag (chutes)) without
exceeding that tensile strength. Add in the mile to get the sled up
to speed, and it looks like
Bonneville *might* have enough room.

I would guess that this is not impossible, but I do have doubts about
about it being practical.

/dps

Earl Colby Pottinger wrote:
[...]
None of those considerations prevent the use of a land based powered landing
sled that matchs speed and ground track with the landing craft (note I don't
assume it is without any power) thus saving more weight.

Note: the feedback system to make the sled track the landing craft can be as
simple as a laser directed downwards from the base of the landing craft and a
set of sensors on the sled insure that the beam is always held in the center
of the landing sled's platform.

I suspect that at "reasonable" landing speeds, the lateral tracking of
the sled will be limited by how tight a turn it can make before it
starts tipping. Of course, a wide-and-low sled won't tip *over* very
easily, but it will probably tip enough to affect wheel loading, which
may feed into speed control as well as steering forces.

And I also suspect that the difference in speed between lander and
sled has to be *very* small to avoid in-track shear forces, and the
sled may have to be *very* heavy to avoid the lander's lift from
picking it up, which implies tensile strength for the capture.

Then there's the length of the landing strip. It needs to be long
enough to be able to brake (w/wheels or drag (chutes)) without
exceeding that tensile strength. Add in the mile to get the sled up
to speed, and it looks like
Bonneville *might* have enough room.

I would guess that this is not impossible, but I do have doubts about
about it being practical.

/dps

Earl Colby Pottinger wrote in message ...
Thinking about the problem some more it seems a big problem would be landing
a high speed glider onto a sled that is on tracks. This would mean that the
sled could only control it's movements in one dimension. A bad cross wind or
gust leaves the glider to do all the working of correction with it's limited
energy budget. If instead the sled is a wheeled platform then it can follow
the glider's movements instead.

Why wheels? Use a hovercraft as your sled.

Designed to operate in a place like salt flats, Utah, it may bear more
resemblance to an industrial hover-skate for heavy loads than to a
hovercraft in the english channel. It can match the returning
vehicle's velocity on two dimensions and absorb much of the vertical
velocity using a cradle cushioned with large, leaky, air bags inflated
by the same fans that generate lift.

The same hovercraft can be used for takeoff (possibly with a different
cradle configuration and boosters). There is no need for special
runways or reinforced pavement. With an air cushion and plenty of room
to accelerate (and decelerate) it can reach very high speeds and
reduce the size and weight of the wings.

Earl Colby Pottinger wrote in message ...
Thinking about the problem some more it seems a big problem would be landing
a high speed glider onto a sled that is on tracks. This would mean that the
sled could only control it's movements in one dimension. A bad cross wind or
gust leaves the glider to do all the working of correction with it's limited
energy budget. If instead the sled is a wheeled platform then it can follow
the glider's movements instead.

Why wheels? Use a hovercraft as your sled.

Designed to operate in a place like salt flats, Utah, it may bear more
resemblance to an industrial hover-skate for heavy loads than to a
hovercraft in the english channel. It can match the returning
vehicle's velocity on two dimensions and absorb much of the vertical
velocity using a cradle cushioned with large, leaky, air bags inflated
by the same fans that generate lift.

The same hovercraft can be used for takeoff (possibly with a different
cradle configuration and boosters). There is no need for special
runways or reinforced pavement. With an air cushion and plenty of room
to accelerate (and decelerate) it can reach very high speeds and
reduce the size and weight of the wings.

(Oren Tirosh) :

Why wheels? Use a hovercraft as your sled.

Well developed tech. Easy to get up to speed. Easy to design brakes for.
Braking a hovercraft is going to be a pain.

Designed to operate in a place like salt flats, Utah, it may bear more
resemblance to an industrial hover-skate for heavy loads than to a
hovercraft in the english channel. It can match the returning
vehicle's velocity on two dimensions and absorb much of the vertical
velocity using a cradle cushioned with large, leaky, air bags inflated
by the same fans that generate lift.

Yes about the landing bags, I was starting to think of that too. Made of a
higher temperature material like fiberglass the landing craft does not even
need to be completely cooled down before landing.

The same hovercraft can be used for takeoff (possibly with a different
cradle configuration and boosters). There is no need for special
runways or reinforced pavement. With an air cushion and plenty of room
to accelerate (and decelerate) it can reach very high speeds and
reduce the size and weight of the wings.

The same applies for a wheeled design. Still nothing is carved in stone here.

Earl Colby Pottinger

--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp

(dave schneider) :

I suspect that at "reasonable" landing speeds, the lateral tracking of
the sled will be limited by how tight a turn it can make before it
starts tipping. Of course, a wide-and-low sled won't tip *over* very
easily, but it will probably tip enough to affect wheel loading, which
may feed into speed control as well as steering forces.

First, what do you consider reasonable? 100-200 KPH are easy speeds for a
wheeled platform to reach and maintain. Second, what tight turns? Where do
you see aircraft come in for a landing where they are not just basicly moving
in a straight line? So why would tracking be a problem? By the way don't
forget all-wheel steering.

And I also suspect that the difference in speed between lander and
sled has to be *very* small to avoid in-track shear forces, and the
sled may have to be *very* heavy to avoid the lander's lift from
picking it up, which implies tensile strength for the capture.

I don't think you are thinking of the same thing/design as me. In the final
seconds of landing there would be *zero* land speed diffirence between the
sled and the landing craft. The lander is in affect is lowering itself onto
the sled.

Why would the lander lift the sled? As soon as it lands it does the same
thing all airplanes do to stay on the runway and not take off again.

Then there's the length of the landing strip. It needs to be long
enough to be able to brake (w/wheels or drag (chutes)) without
exceeding that tensile strength. Add in the mile to get the sled up
to speed, and it looks like Bonneville *might* have enough room.

??? North America atleast has tons of flat open space to drive such a craft.
Also someone else has suggested making the sled a hovercraft which makes
every large lake a landing site.

The Bonneville reference means nothing to me. What is that in reference to?

I would guess that this is not impossible, but I do have doubts about
about it being practical.

I doubt it is practical but to me your objections did not seem well founded.
(Tight turns?)

Earl Colby Pottinger

--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp

(Len) :

Earl Colby Pottinger wrote in message
...

In the case of a flying sled can they be brought together without the
airflow between the two crafts messing up the fine control needed?

With air recovery, a tow line is an option--and that can avoid
airflow intereactions.

But now the landing craft needs to carry it's landing gear, that is what I
was trying to avoid.

Back in the early 1960s, when I was project engineer for
space transportation systems at North American/LA Div.,
we looked at towing an upper stage package with the B-70
in order to avoid airflow interactions, and also to get
a bigger lump through the drag rise. The B-70 bombbay
was not large enough to carry a very big upper stage
package--although I think that the Agena fit. (Lockheed
had contacted us about launching Agena from the B-70.
Although they were interested in the performance booost,
their main motivation--even back in the early 1960s--was
an excuse to get away from the official launch complexes
like the Cape).

The early Discover(?) satellite capsules were recovered
with a C-130. This sort of worked even though the capsule
was traveling vertically (from a parachute) and the C-130
was basically traveling horizontally.

Were they very heavy?

Best regards,
Len (Cormier)
PanAero, Inc.
(replace x with len) ( http://www.tour2space.com )

Earl Colby Pottinger

--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp